Systems and methods for inferring barometric pressure

ABSTRACT

Methods and systems are provided for determining barometric pressure. In one example, an onboard vacuum pump is utilized to draw a vacuum at a constant flow rate across a reference orifice, and the resulting vacuum level is converted to a barometric pressure. In this way, other sensors for determining barometric pressure in a vehicle may be rationalized without the use of engine operation, and in an example where the other sensors for determining barometric pressure are not functioning as desired, barometric pressure as inferred from the onboard pump may be utilized to adjust engine operation.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 15/211,856, entitled “SYSTEMS AND METHODS FOR INFERRINGBAROMETRIC PRESSURE,” filed on Jul. 15, 2016. The entire contents of theabove-referenced application are hereby incorporated by reference in itsentirety for all purposes.

FIELD

The present description relates generally to methods and systems forcontrolling a vehicle evaporative level check module (ELCM) pump toinfer barometric pressure.

BACKGROUND/SUMMARY

Barometric pressure (BP) in an engine intake of a vehicle may vary dueto altitude changes of the vehicle. Thus, an accurate assessment ofbarometric pressure changes experienced by an engine of a vehicle may bebeneficial for improved operation of the vehicle. In particular,diagnostic functions, e.g., evaporative emission control systemdiagnostics, and engine strategies, e.g., air/fuel ratio estimates andspark timing, may benefit from having an accurate estimate of barometricpressure. Barometric pressure is typically determined via either adedicated BP sensor, or inferred via a manifold absolute pressure (MAP)sensor positioned in an intake of the engine. However, in a conditionwhere the BP sensor is not functioning as desired, or if the BPinference is not correct, such a condition may have adverse effects onengine controls and other diagnostics that utilize the BP data.Accordingly, the BP sensor or surrogate MAP sensor needs to berationalized per California Air Resources Board (CARE) regulations.

Prior art methods may utilize other engine pressure sensors torationalize BP. For example, U.S. patent application 7,631,552 teaches afault condition when the absolute pressure differential between intakemanifold pressure and barometric pressure exceeds a calibratable maximumthreshold, for a calibratable period of time and a calibratable numberof occurrences and a calibratable number of drive cycles. However, theinventors have recognized potential issues with such an approach. As oneexample, in a case where a vehicle is not equipped with a dedicated BPsensor, but rather BP is being inferred from a MAP sensor, there may belimited options for rationality to other engine sensors. Furthermore, insome approaches a global positioning system (GPS) may be included in avehicle to determine altitude changes. However, not all vehicles haveGPS technology and there may be remote geographical areas where GPSreception is not available. As such, rationalizing BP via GPS technologymay be unreliable or costly.

Thus, the inventors herein have developed systems and methods to atleast partially address the above issues. In one example a method isprovided, comprising delivering fuel from a fuel system to an enginepropelling a vehicle; storing fuel vapors from the fuel system in anevaporative emissions control system; determining an estimate ofbarometric pressure as a function of an efficiency of a vacuum pumpconfigured to evacuate or pressurize the fuel system and evaporativeemissions control system; and adjusting a vehicle operating parameterresponsive to the estimate.

As one example, determining an estimate of barometric pressure as afunction of the efficiency of the vacuum pump includes turning on thevacuum pump and drawing a vacuum across a reference orifice of fixeddiameter. The efficiency of the vacuum pump is thus a function of avacuum level achieved by the vacuum pump when drawing the vacuum acrossthe reference orifice of fixed diameter. In an example, efficiency ofthe vacuum pump decreases as barometric pressure decreases, andefficiency of the vacuum pump increases as barometric pressureincreases. Barometric pressure determined as the function of theefficiency of the vacuum pump is thus correlated with barometricpressure determined from one or more sensor(s) in the vehicle, whereinit is indicated that the one or more sensors in the vehicle are notfunctioning as desired responsive to a lack of correlation betweenbarometric pressure determined as the function of the efficiency of thevacuum pump and barometric pressure determined from the one or moresensor(s) in the vehicle. In this way, barometric pressure may beinferred by a pump wherein a reference vacuum is drawn across areference orifice. By inferring barometric pressure using a pump, otherbarometric pressure sensor(s) in the vehicle may be rationalized,whereby engine strategies that benefit from an accurate estimate ofbarometric pressure may be improved.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an example vehicle propulsion system.

FIG. 2 schematically shows an example vehicle system with a fuel systemand an evaporative emissions system.

FIG. 3A shows a schematic depiction of an evaporative level check module(ELCM) in a configuration to perform a reference check.

FIG. 3B shows a schematic depiction of an ELCM in a configuration toevacuate a fuel system and evaporative emissions system.

FIG. 3C shows a schematic depiction of an ELCM in a configuration thatcouples a fuel vapor canister to atmosphere.

FIG. 3D shows a schematic depiction of an ELCM in a configuration topressurize a fuel system and evaporative emissions system.

FIGS. 4A-4B show a schematic depiction of an electronic circuitconfigured to reverse the spin orientation of an electric motor.

FIG. 5A schematically shows an example timeline for conducting anevaporative emissions test diagnostic by evacuating an evaporativeemissions system.

FIG. 5B schematically shows an example timeline for conducting anELCM-based barometric pressure (BP) measurement.

FIG. 6 shows a high level flow chart for conducting an ELCM-based BPmeasurement and a BP sensor rationalization procedure.

FIG. 7 shows a high level flow chart for controlling vehicle operationresponsive to an indication that a BP sensor is not functioning asdesired.

FIG. 8 shows a timeline for conducting a BP rationalization procedureand for controlling vehicle operation responsive to an indication that aBP sensor is not functioning as desired.

DETAILED DESCRIPTION

The following description relates to systems and methods for conductinga barometric pressure (BP) rationalization procedure via the use of anevaporative level check module (ELCM). Such a rationalization proceduremay be conducted on a vehicle, such as the hybrid vehicle systemdepicted in FIG. 1. However, while FIG. 1 depicts a hybrid vehiclesystem, it may be understood that the systems and methods describedherein are not limited to hybrid vehicle systems. The BP rationalizationprocedure may be conducted using an ELCM pump (or other onboard pump)positioned in an evaporative emissions control system of the vehicle,where the ELCM pump is configured to pressurize or evacuate theevaporative emissions control system and fuel system, such as theevaporative emissions control system and fuel system coupled to anengine system as depicted in FIG. 2. The ECLM may include a referenceorifice, such that when the pump is activated in a first direction andan ELCM changeover valve (COV) is off (e.g. first position), a vacuummay be drawn across the reference orifice in order to indicate areference vacuum level, indicated by the ELCM configuration depicted inFIG. 3A. The reference vacuum level may be linearly correlated with BP,thus providing an estimate of BP. When the ELCM pump is turned on in thefirst direction and the ELCM COV turned on (e.g., second position), thefuel system and evaporative emissions system may be evacuated to conductan evaporative emissions test diagnostic, as shown by the configurationdepicted in FIG. 3B. When the ELCM pump is turned off and the ELCM COVis also off (e.g., first position), a fuel vapor canister may be coupledto atmosphere, as shown by the configuration depicted in FIG. 3C. Whenthe ELCM pump is turned on in a second direction and the ELCM COV isturned on (e.g., second position), the fuel system and evaporativeemissions system may be pressurized to conduct an evaporative emissionstest diagnostic, as shown by the configuration depicted in FIG. 3D.

The ELCM pump may include a motor that is reversible by means of anH-bridge circuit, as shown in FIGS. 4A-4B. A typical ELCM-basedevaporative emissions test diagnostic may be conducted as shown by theexample timeline depicted in FIG. 5A. The ELCM may be additionally usedto conduct the ELCM-based BP measurement, illustrated by the exampletimeline depicted in FIG. 5B. An ELCM-based BP measurement and BPrationalization procedure may be conducted according to the methodillustrated in FIG. 6. Responsive to an indication that a BP sensor isnot functioning as desired, vehicle operating conditions may be adjustedbased on the method illustrated in FIG. 7. A timeline for conducting anELCM-based BP measurement and BP rationalization procedure, along withadjusting vehicle operating conditions responsive to an indication thatthe BP sensor is not functioning as desired, is illustrated in FIG. 8.

FIG. 1 illustrates an example vehicle propulsion system 100. Vehiclepropulsion system 100 includes a fuel burning engine 110 and a motor120. As a non-limiting example, engine 110 comprises an internalcombustion engine and motor 120 comprises an electric motor. Motor 120may be configured to utilize or consume a different energy source thanengine 110. For example, engine 110 may consume a liquid fuel (e.g.,gasoline) to produce an engine output while motor 120 may consumeelectrical energy to produce a motor output. As such, a vehicle withpropulsion system 100 may be referred to as a hybrid electric vehicle(HEV).

Vehicle propulsion system 100 may utilize a variety of differentoperational modes depending on operating conditions encountered by thevehicle propulsion system. Some of these modes may enable engine 110 tobe maintained in an off state (i.e. set to a deactivated state) wherecombustion of fuel at the engine is discontinued. For example, underselect operating conditions, motor 120 may propel the vehicle via drivewheel 130 as indicated by arrow 122 while engine 110 is deactivated.

During other operating conditions, engine 110 may be set to adeactivated state (as described above) while motor 120 may be operatedto charge energy storage device 150. For example, motor 120 may receivewheel torque from drive wheel 130 as indicated by arrow 122 where themotor may convert the kinetic energy of the vehicle to electrical energyfor storage at energy storage device 150 as indicated by arrow 124. Thisoperation may be referred to as regenerative braking of the vehicle.Thus, motor 120 can provide a generator function in some embodiments.However, in other embodiments, generator 160 may instead receive wheeltorque from drive wheel 130, where the generator may convert the kineticenergy of the vehicle to electrical energy for storage at energy storagedevice 150 as indicated by arrow 162. During still other operatingconditions, engine 110 may be operated by combusting fuel received fromfuel system 140 as indicated by arrow 142. For example, engine 110 maybe operated to propel the vehicle via drive wheel 130 as indicated byarrow 112 while motor 120 is deactivated. During other operatingconditions, both engine 110 and motor 120 may each be operated to propelthe vehicle via drive wheel 130 as indicated by arrows 112 and 122,respectively. A configuration where both the engine and the motor mayselectively propel the vehicle may be referred to as a parallel typevehicle propulsion system. Note that in some embodiments, motor 120 maypropel the vehicle via a first set of drive wheels and engine 110 maypropel the vehicle via a second set of drive wheels.

In other embodiments, vehicle propulsion system 100 may be configured asa series type vehicle propulsion system, whereby the engine does notdirectly propel the drive wheels. Rather, engine 110 may be operated topower motor 120, which may in turn propel the vehicle via drive wheel130 as indicated by arrow 122. For example, during select operatingconditions, engine 110 may drive generator 160, which may in turn supplyelectrical energy to one or more of motor 120 as indicated by arrow 114or energy storage device 150 as indicated by arrow 162. As anotherexample, engine 110 may be operated to drive motor 120 which may in turnprovide a generator function to convert the engine output to electricalenergy, where the electrical energy may be stored at energy storagedevice 150 for later use by the motor.

Fuel system 140 may include one or more fuel storage tanks 144 forstoring fuel on-board the vehicle. For example, fuel tank 144 may storeone or more liquid fuels, including but not limited to: gasoline,diesel, and alcohol fuels. In some examples, the fuel may be storedon-board the vehicle as a blend of two or more different fuels. Forexample, fuel tank 144 may be configured to store a blend of gasolineand ethanol (e.g., E10, E85, etc.) or a blend of gasoline and methanol(e.g., M10, M85, etc.), whereby these fuels or fuel blends may bedelivered to engine 110 as indicated by arrow 142. Still other suitablefuels or fuel blends may be supplied to engine 110, where they may becombusted at the engine to produce an engine output. The engine outputmay be utilized to propel the vehicle as indicated by arrow 112 or torecharge energy storage device 150 via motor 120 or generator 160.

In some embodiments, energy storage device 150 may be configured tostore electrical energy that may be supplied to other electrical loadsresiding on-board the vehicle (other than the motor), including cabinheating and air conditioning, engine starting, headlights, cabin audioand video systems, etc. As a non-limiting example, energy storage device150 may include one or more batteries and/or capacitors.

Control system 190 may communicate with one or more of engine 110, motor120, fuel system 140, energy storage device 150, and generator 160. Forexample, control system 190 may receive sensory feedback informationfrom one or more of engine 110, motor 120, fuel system 140, energystorage device 150, and generator 160. Further, control system 190 maysend control signals to one or more of engine 110, motor 120, fuelsystem 140, energy storage device 150, and generator 160 responsive tothis sensory feedback. Control system 190 may receive an indication ofan operator requested output of the vehicle propulsion system from avehicle operator 102. For example, control system 190 may receivesensory feedback from pedal position sensor 194 which communicates withpedal 192. Pedal 192 may refer schematically to a brake pedal and/or anaccelerator pedal.

Energy storage device 150 may periodically receive electrical energyfrom a power source 180 residing external to the vehicle (e.g., not partof the vehicle) as indicated by arrow 184. As a non-limiting example,vehicle propulsion system 100 may be configured as a plug-in hybridelectric vehicle (HEV), whereby electrical energy may be supplied toenergy storage device 150 from power source 180 via an electrical energytransmission cable 182. During a recharging operation of energy storagedevice 150 from power source 180, electrical transmission cable 182 mayelectrically couple energy storage device 150 and power source 180.While the vehicle propulsion system is operated to propel the vehicle,electrical transmission cable 182 may disconnected between power source180 and energy storage device 150. Control system 190 may identifyand/or control the amount of electrical energy stored at the energystorage device, which may be referred to as the state of charge (SOC).

In other embodiments, electrical transmission cable 182 may be omitted,where electrical energy may be received wirelessly at energy storagedevice 150 from power source 180. For example, energy storage device 150may receive electrical energy from power source 180 via one or more ofelectromagnetic induction, radio waves, and electromagnetic resonance.As such, it should be appreciated that any suitable approach may be usedfor recharging energy storage device 150 from a power source that doesnot comprise part of the vehicle. In this way, motor 120 may propel thevehicle by utilizing an energy source other than the fuel utilized byengine 110.

Fuel system 140 may periodically receive fuel from a fuel sourceresiding external to the vehicle. As a non-limiting example, vehiclepropulsion system 100 may be refueled by receiving fuel via a fueldispensing device 170 as indicated by arrow 172. In some embodiments,fuel tank 144 may be configured to store the fuel received from fueldispensing device 170 until it is supplied to engine 110 for combustion.In some embodiments, control system 190 may receive an indication of thelevel of fuel stored at fuel tank 144 via a fuel level sensor. The levelof fuel stored at fuel tank 144 (e.g., as identified by the fuel levelsensor) may be communicated to the vehicle operator, for example, via afuel gauge or indication in a vehicle instrument panel 196.

The vehicle propulsion system 100 may also include an ambienttemperature/humidity sensor 198, and a roll stability control sensor,such as a lateral and/or longitudinal and/or yaw rate sensor(s) 199. Thevehicle instrument panel 196 may include indicator light(s) and/or atext-based display in which messages are displayed to an operator. Thevehicle instrument panel 196 may also include various input portions forreceiving an operator input, such as buttons, touch screens, voiceinput/recognition, etc. For example, the vehicle instrument panel 196may include a refueling button 193 which may be manually actuated orpressed by a vehicle operator to initiate refueling. For example, asdescribed in more detail below, in response to the vehicle operatoractuating refueling button 193, a fuel tank in the vehicle may bedepressurized so that refueling may be performed.

In an alternative example, the vehicle instrument panel 196 maycommunicate audio messages to the operator without display. Further, thesensor(s) 199 may include a vertical accelerometer to indicate roadroughness. These devices may be connected to control system 190. In oneexample, the control system may adjust engine output and/or the wheelbrakes to increase vehicle stability in response to sensor(s) 199.

One or more tire pressure monitoring sensors (TPMS) may be coupled toone or more tires of wheels in the vehicle. For example, FIG. 1 shows atire pressure sensor 197 coupled to wheel 130 and configured to monitora pressure in a tire 131 of wheel 130. As described in more detailbelow, tire pressure sensors can be used as an auxiliary source fordetermining a change in barometric pressure. For example, a tirepressure change may indicate an increase or decrease in vehiclealtitude. Furthermore, in some examples, vehicle propulsion system 100may include a pneumatic control unit 123. Pneumatic control unit mayreceive information regarding tire pressure from tire pressure sensor(s)197, and send said tire pressure information to control system 190.Based on said tire pressure information, control system 190 may commandpneumatic control unit 123 to inflate or deflate tire(s) 131. Forexample, responsive to an indication of a tire pressure decrease,control system 190 may command pneumatic control system unit 123 toinflate tire(s) 131. Alternatively, responsive to an indication of atire pressure increase, control system 190 may command pneumatic controlsystem unit 123 to deflate tire(s) 131. In both examples, pneumaticcontrol system unit 123 may be used to inflate or deflate tires 131 toan optimal tire pressure rating for said tires, which may prolong tirelife. Furthermore, it may be understood that a tire pressure increasemay result from a decrease in barometric pressure, whereas a tirepressure decrease may result from an increase in barometric pressure. Assuch, pneumatic control system unit 123 may be used in some examples toadjust tire pressure to optimal tire pressure rating, as a function ofbarometric pressure changes, the barometric pressure changes in someexamples a result of altitude change.

FIG. 2 shows a schematic depiction of a vehicle system 206. The vehiclesystem 206 includes an engine system 208 coupled to an emissions controlsystem 251 and a fuel system 218. Emission control system 251 includes afuel vapor container or canister 222 which may be used to capture andstore fuel vapors. In some examples, vehicle system 206 may be a hybridelectric vehicle system.

The engine system 208 may include an engine 210 having a plurality ofcylinders 230. The engine 210 includes an engine intake 223 and anengine exhaust 225. The engine intake 223 includes a throttle 262fluidly coupled to the engine intake manifold 244 via an intake passage242. Engine intake may further include various sensors. For example, amass air flow (MAF) sensor 202 may be coupled to the engine intake todetermine a rate of air mass flowing through the intake. Further, abarometric pressure sensor 213 may be included in the engine intake. Forexample, barometric pressure sensor 213 may be a manifold air pressure(MAP) sensor and may be coupled to the engine intake downstream ofthrottle 262. Barometric pressure sensor 213 may rely on part throttleor full or wide open throttle conditions, e.g., when an opening amountof throttle 262 is greater than a threshold, in order accuratelydetermine BP.

The engine exhaust 225 includes an exhaust manifold 248 leading to anexhaust passage 235 that routes exhaust gas to the atmosphere. Theengine exhaust 225 may include one or more emission control devices 270,which may be mounted in a close-coupled position in the exhaust. One ormore emission control devices may include a three-way catalyst, lean NOxtrap, diesel particulate filter, oxidation catalyst, etc. It will beappreciated that other components may be included in the engine such asa variety of valves and sensors.

Fuel system 218 may include a fuel tank 220 coupled to a fuel pumpsystem 221. The fuel pump system 221 may include one or more pumps forpressurizing fuel delivered to the injectors of engine 210, such as theexample injector 266 shown. While only a single injector 266 is shown,additional injectors are provided for each cylinder. It will beappreciated that fuel system 218 may be a return-less fuel system, areturn fuel system, or various other types of fuel system. Fuel tank 220may hold a plurality of fuel blends, including fuel with a range ofalcohol concentrations, such as various gasoline-ethanol blends,including E10, E85, gasoline, etc., and combinations thereof. A fuellevel sensor 234 located in fuel tank 220 may provide an indication ofthe fuel level (“Fuel Level Input”) to controller 212. As depicted, fuellevel sensor 234 may comprise a float connected to a variable resistor.Alternatively, other types of fuel level sensors may be used.

Vapors generated in fuel system 218 may be routed to an evaporativeemissions control system 251 which includes a fuel vapor canister 222via vapor recovery line 231, before being purged to the engine intake223. Vapor recovery line 231 may be coupled to fuel tank 220 via one ormore conduits and may include one or more valves for isolating the fueltank during certain conditions. For example, vapor recovery line 231 maybe coupled to fuel tank 220 via one or more or a combination of conduits271, 273, and 275.

Further, in some examples, one or more fuel tank vent valves in conduits271, 273, or 275. Among other functions, fuel tank vent valves may allowa fuel vapor canister of the emissions control system to be maintainedat a low pressure or vacuum without increasing the fuel evaporation ratefrom the tank (which would otherwise occur if the fuel tank pressurewere lowered). For example, conduit 271 may include a grade vent valve(GVV) 287, conduit 273 may include a fill limit venting valve (FLVV)285, and conduit 275 may include a grade vent valve (GVV) 283. Further,in some examples, recovery line 231 may be coupled to a fuel fillersystem 219. In some examples, fuel filler system may include a fuel cap205 for sealing off the fuel filler system from the atmosphere.Refueling system 219 is coupled to fuel tank 220 via a fuel filler pipeor neck 211.

Further, refueling system 219 may include refueling lock 245. In someembodiments, refueling lock 245 may be a fuel cap locking mechanism. Thefuel cap locking mechanism may be configured to automatically lock thefuel cap in a closed position so that the fuel cap cannot be opened. Forexample, the fuel cap 205 may remain locked via refueling lock 245 whilepressure or vacuum in the fuel tank is greater than a threshold. Inresponse to a refuel request, e.g., a vehicle operator initiatedrequest, the fuel tank may be depressurized and the fuel cap unlockedafter the pressure or vacuum in the fuel tank falls below a threshold. Afuel cap locking mechanism may be a latch or clutch, which, whenengaged, prevents the removal of the fuel cap. The latch or clutch maybe electrically locked, for example, by a solenoid, or may bemechanically locked, for example, by a pressure diaphragm.

In some embodiments, refueling lock 245 may be a filler pipe valvelocated at a mouth of fuel filler pipe 211. In such embodiments,refueling lock 245 may not prevent the removal of fuel cap 205. Rather,refueling lock 245 may prevent the insertion of a refueling pump intofuel filler pipe 211. The filler pipe valve may be electrically locked,for example by a solenoid, or mechanically locked, for example by apressure diaphragm.

In some embodiments, refueling lock 245 may be a refueling door lock,such as a latch or a clutch which locks a refueling door located in abody panel of the vehicle. The refueling door lock may be electricallylocked, for example by a solenoid, or mechanically locked, for exampleby a pressure diaphragm.

In embodiments where refueling lock 245 is locked using an electricalmechanism, refueling lock 245 may be unlocked by commands fromcontroller 212, for example, when a fuel tank pressure decreases below apressure threshold. In embodiments where refueling lock 245 is lockedusing a mechanical mechanism, refueling lock 245 may be unlocked via apressure gradient, for example, when a fuel tank pressure decreases toatmospheric pressure.

Emissions control system 251 may include one or more emissions controldevices, such as one or more fuel vapor canisters 222 filled with anappropriate adsorbent, the canisters are configured to temporarily trapfuel vapors (including vaporized hydrocarbons) during fuel tankrefilling operations and “running loss” (that is, fuel vaporized duringvehicle operation). In one example, the adsorbent used is activatedcharcoal. Emissions control system 251 may further include a canisterventilation path or vent line 227 which may route gases out of thecanister 222 to the atmosphere when storing, or trapping, fuel vaporsfrom fuel system 218.

Canister 222 may include a buffer 222a (or buffer region), each of thecanister and the buffer comprising the adsorbent. As shown, the volumeof buffer 222a may be smaller than (e.g., a fraction of) the volume ofcanister 222. The adsorbent in the buffer 222a may be same as, ordifferent from, the adsorbent in the canister (e.g., both may includecharcoal). Buffer 222a may be positioned within canister 222 such thatduring canister loading, fuel tank vapors are first adsorbed within thebuffer, and then when the buffer is saturated, further fuel tank vaporsare adsorbed in the canister. In comparison, during canister purging,fuel vapors are first desorbed from the canister (e.g., to a thresholdamount) before being desorbed from the buffer. In other words, loadingand unloading of the buffer is not linear with the loading and unloadingof the canister. As such, the effect of the canister buffer is to dampenany fuel vapor spikes flowing from the fuel tank to the canister,thereby reducing the possibility of any fuel vapor spikes going to theengine. One or more temperature sensors 232 may be coupled to and/orwithin canister 222. As fuel vapor is adsorbed by the adsorbent in thecanister, heat is generated (heat of adsorption). Likewise, as fuelvapor is desorbed by the adsorbent in the canister, heat is consumed. Inthis way, the adsorption and desorption of fuel vapor by the canistermay be monitored and estimated based on temperature changes within thecanister.

Vent line 227 may also allow fresh air to be drawn into canister 222when purging stored fuel vapors from fuel system 218 to engine intake223 via purge line 228 and purge valve 261. For example, purge valve 261may be normally closed but may be opened during certain conditions sothat vacuum from engine intake manifold 244 is provided to the fuelvapor canister for purging. In some examples, vent line 227 may includean air filter 259 disposed therein upstream of a canister 222.

In some examples, the flow of air and vapors between canister 222 andthe atmosphere may be regulated by a canister vent valve coupled withinvent line 227. When included, the canister vent valve may be a normallyopen valve, so that fuel tank isolation valve 252 (FTIV) may controlventing of fuel tank 220 with the atmosphere. FTIV 252 may be positionedbetween the fuel tank and the fuel vapor canister within conduit 278.FTIV 252 may be a normally closed valve, that when opened, allows forthe venting of fuel vapors from fuel tank 220 to canister 222. Fuelvapors may then be vented to atmosphere, or purged to engine intakesystem 223 via canister purge valve 261.

Fuel system 218 may be operated by controller 212 in a plurality ofmodes by selective adjustment of the various valves and solenoids. Forexample, the fuel system may be operated in a fuel vapor storage mode(e.g., during a fuel tank refueling operation and with the engine notrunning), wherein the controller 212 may open isolation valve 252 whileclosing canister purge valve (CPV) 261 to direct refueling vapors intocanister 222 while preventing fuel vapors from being directed into theintake manifold.

As another example, the fuel system may be operated in a refueling mode(e.g., when fuel tank refueling is requested by a vehicle operator),wherein the controller 212 may open isolation valve 252, whilemaintaining canister purge valve 261 closed, to depressurize the fueltank before allowing enabling fuel to be added therein. As such,isolation valve 252 may be kept open during the refueling operation toallow refueling vapors to be stored in the canister. After refueling iscompleted, the isolation valve may be closed.

As yet another example, the fuel system may be operated in a canisterpurging mode (e.g., after an emission control device light-offtemperature has been attained and with the engine running), wherein thecontroller 212 may open canister purge valve 261 while closing isolationvalve 252. Herein, the vacuum generated by the intake manifold of theoperating engine may be used to draw fresh air through vent 27 andthrough fuel vapor canister 22 to purge the stored fuel vapors intointake manifold 44. In this mode, the purged fuel vapors from thecanister are combusted in the engine. The purging may be continued untilthe stored fuel vapor amount in the canister is below a threshold.

Controller 212 may comprise a portion of a control system 214. Controlsystem 214 is shown receiving information from a plurality of sensors216 (various examples of which are described herein) and sending controlsignals to a plurality of actuators 281 (various examples of which aredescribed herein). As one example, sensors 216 may include exhaust gassensor 237 located upstream of the emission control device, temperaturesensor 233, pressure sensor 291, MAF sensor 202, MAP sensor 213, andcanister temperature sensor 232. Other sensors such as pressure,temperature, air/fuel ratio, and composition sensors may be coupled tovarious locations in the vehicle system 206. As another example, theactuators may include fuel injector 266, throttle 262, fuel tankisolation valve 253, pump 292, and refueling lock 245. The controlsystem 214 may include a controller 212. The controller may receiveinput data from the various sensors, process the input data, and triggerthe actuators in response to the processed input data based oninstruction or code programmed therein corresponding to one or moreroutines. Example control routines are described herein with regard toFIGS. 6 and 7.

Evaporative emissions test diagnostic routines may be intermittentlyperformed by controller 212 on fuel system 218 and evaporative emissionscontrol system 251 to confirm the presence or absence of undesiredevaporative emissions. As such, evaporative emissions test diagnosticroutines may be performed while the engine is off (engine-off test)using engine-off natural vacuum (EONV) generated due to a change intemperature and pressure at the fuel tank following engine shutdownand/or with vacuum supplemented from a vacuum pump. Alternatively,evaporative emissions test diagnostic routines may be performed whilethe engine is running by operating a vacuum pump and/or using engineintake manifold vacuum. Evaporative emissions test diagnostics may beperformed by an evaporative level check module (ELCM) 295communicatively coupled to controller 212. ELCM 295 may be coupled invent 227, between canister 222 and the atmosphere. ELCM 295 may includea vacuum pump for applying negative pressure to the fuel system whenadministering a evaporative emissions test. In some embodiments, thevacuum pump may be configured to be reversible. In other words, thevacuum pump may be configured to apply either a negative pressure or apositive pressure on the evaporative emissions system 251 and fuelsystem 218. ELCM 295 may further include a reference orifice and apressure sensor 296. A reference check may thus be performed whereby avacuum may be drawn across the reference orifice, where the resultingvacuum level comprises a vacuum level indicative of an absence ofundesired evaporative emissions. For example, following the referencecheck, the fuel system 218 and evaporative emissions system 251 may beevacuated by the ELCM vacuum pump. In the absence of undesiredevaporative emissions, the vacuum may pull down to the reference checkvacuum level. Alternatively, in the presence of undesired evaporativeemissions, the vacuum may not pull down to the reference check vacuumlevel.

FIGS. 3A-3D show a schematic depiction of an example ELCM 295 in variousconditions in accordance with the present disclosure. As shown in FIG.2, ELCM 295 may be located along vent 227 between canister 222 andatmosphere. ELCM 295 includes a changeover valve (COV) 315, a pump 330,and a pressure sensor 296. Pump 330 may be a reversible pump, forexample, a vane pump. COV 315 may be moveable between a first a secondposition. In the first position, as shown in FIGS. 3A and 3C, air mayflow through ELCM 295 via first flow path 320. In the second position,as shown in FIGS. 3B and 3D, air may flow through ELCM 295 via secondflow path 325. The position of COV 315 may be controlled by solenoid 310via compression spring 305. ELCM 295 may also comprise reference orifice340. Reference orifice 340 may have a diameter corresponding to the sizeof a threshold for undesired evaporative emissions to be tested, forexample, 0.02″. In either the first or second position, pressure sensor296 may generate a pressure signal reflecting the pressure within ELCM295. Operation of pump 330 and solenoid 310 may be controlled viasignals received from controller 212. As will be discussed in furtherdetail below, in addition to being utilized in order to conduct anevaporative emissions test diagnostic procedure, the ELCM may be used toinfer barometric pressure (BP). Briefly, the pump 330 may be activatedto draw a vacuum across the reference orifice 340. The level of vacuumachieved may be linearly correlated with BP. In other words, the ELCMpump may be more efficient at lower altitudes and less efficient athigher altitudes. As such, a BP may be inferred based on a vacuum levelindicated during drawing a vacuum across the reference orifice 340.

As shown in FIG. 3A, COV 315 is in the first position, and pump 330 isactivated in a first direction. Air flow through ELCM 295 in thisconfiguration is represented by arrows. In this configuration, pump 330may draw a vacuum on reference orifice 340, and pressure sensor 296 mayrecord the vacuum level within ELCM 295. This reference check vacuumlevel reading may then become the threshold for the presence or absenceof undesired evaporative emissions in a subsequent evaporative emissionstest diagnostic. Furthermore, discussed above and which will bediscussed in further detail below, an ELCM-based BP measurement may beconducted based on the reference vacuum level, where the referencevacuum level may be used to infer a BP, and where the inferred BP may beused to rationalize a BP sensor (e.g., 213). For example, efficiency ofthe pump (e.g., onboard vacuum pump) is a function of the vacuum levelachieved by the vacuum pump when drawing the vacuum across the referenceorifice of fixed diameter. As such, efficiency of the vacuum pumpdecreases as barometric pressure decreases, whereas efficiency of thevacuum pump increases as barometric pressure increases. In other words,the vacuum level reached during activating the onboard vacuum pump todraw the vacuum across the reference orifice is linearly correlated withbarometric pressure. As such, a method is described below (FIG. 6)describing correlating barometric pressure determined as the function ofthe efficiency of the vacuum pump with barometric pressure determinedfrom one or more sensor(s) in the vehicle. For example, the method mayinclude indicating the one or more sensor(s) in the vehicle are notfunctioning as desired responsive to a lack of correlation betweenbarometric pressure determined as the function of the efficiency of thevacuum pump and barometric pressure determined from the one or moresensor(s) in the vehicle. In some examples, the one or more sensor(s) inthe vehicle may include a manifold absolute pressure sensor coupled toan air intake manifold of the engine. As such, an estimate of barometricpressure may be determined without operation of the vehicle engine, viathe use of an electric onboard vacuum pump.

As shown in FIG. 3B, COV 315 is in the second position, and pump 330 isactivated in the first direction. This configuration allows pump 330 todraw a vacuum on fuel system 218 and evaporative emissions system 251.In examples where fuel system 218 includes FTIV 252, FTIV 252 may beopened to allow pump 330 to draw a vacuum on fuel tank 220. Air flowthrough ELCM 295 in this configuration is represented by arrows. In thisconfiguration, as pump 330 pulls a vacuum on fuel system 218, theabsence of undesired evaporative emissions in the system should allowfor the vacuum level in ELCM 295 to reach or exceed the previouslydetermined reference vacuum threshold. In the presence of undesiredevaporative emissions larger than the reference orifice, the pump willnot pull down to the reference check vacuum level.

As shown in FIG. 3C, COV 315 is in the first position, and pump 330 isde-activated. This configuration allows for air to freely flow betweenatmosphere and the canister. This configuration may be used during acanister purging operation, for example, and may additionally be usedduring vehicle operation when a purging operation is not beingconducted, and when the vehicle is not in operation.

As shown in FIG. 3D, COV 315 is in the second position, and pump 330 isactivated in a second direction, opposite from the first direction. Inthis configuration, pump 330 may pull air from atmosphere into fuelsystem 218 and evaporative emission system 251. In a configuration whereFTIV 252 is open and CPV 261 is closed, air drawn by pump 330 maypromote desorption of fuel vapor from canister 222, and further directthe desorbed fuel vapor into fuel tank 220. In this way, fuel vapor maybe purged from the canister to the fuel tank, thereby decreasing thepotential for bleed emissions.

In summary, drawing a vacuum across the reference orifice of fixeddiameter includes configuring the changeover valve coupled to the vacuumpump in a first position (an OFF configuration), and pressurizing orevacuating the vehicle fuel system and evaporative emissions controlsystem includes configuring the changeover valve in a second position(on ON configuration). FIGS. 4A and 4B show an example circuit 400 thatmay be used for reversing pump motor of ELCM 295. Circuit 400schematically depicts an H-Bridge circuit that may be used to run amotor 410 in a first (forward) direction and alternately in a second(reverse) direction. Circuit 400 comprises a first (LO) side 420 and asecond (HI) side 430. Side 420 includes transistors 421 and 422, whileside 430 includes transistors 431 and 432. Circuit 400 further includesa power source 440.

In FIG. 4A, transistors 421 and 432 are activated, while transistors 422and 431 are off. In this confirmation, the left lead 451 of motor 410 isconnected to power source 440, and the right lead 452 of motor 410 isconnected to ground. In this way, motor 400 may run in a forwarddirection. When operating the engine in a forward direction via themotor, the engine may be in a cranking mode for initial combustioncommencement. Additionally and/or alternatively, when operating theengine in a forward direction via the motor, the engine (and motor oranother motor) may be in a drive mode to drive the vehicle. During oneor more of or each of the forward engine rotation operations, fuelvapors may also be purged to the engine with and/or without enginecombustion occurring.

In FIG. 4B, transistors 422 and 431 are activated, while transistors 421and 432 are off. In this confirmation, the right lead 452 of motor 410is connected to power source 440, and the left lead 451 of motor 410 isconnected to ground. In this way, motor 400 may run in a reversedirection.

FIG. 5 depicts an example timeline 500 for conducting an evaporativeemissions test diagnostic utilizing an evaporative level check module(ELCM) to evacuate a vehicle evaporative emissions control system inorder to conduct an evaporative emissions test diagnostic. While notexplicitly illustrated, it may be understood that, if included, a fueltank isolation valve (FTIV) (e.g., 252) is closed to isolate the fuelsystem from the evaporative emission control system. However, in someexamples, the FTIV may be open, thus coupling the fuel system to theevaporative emissions control system, whereby the evaporative emissionstest diagnostic may be conducted on the fuel system and evaporativeemissions control system. In this example timeline 500, for illustrativepurposes, it may be understood that, if included, the FTIV is closed.Timeline 500 includes plot 505, indicating pressure as monitored, forexample, by an ELCM pressure sensor (e.g., 296), over time. Line 512represents a threshold vacuum level (reference vacuum level) indicatingthe absence of undesired evaporative emissions, discussed in furtherdetail below. Timeline 500 further includes plot 515, indicating an onor off state of the ELCM pump (e.g., 330), over time. Timeline 500further includes plot 520, indicating whether an ELCM changeover valve(COV) (e.g., 315) is in an on (e.g., second position) or off (e.g.,first position) state, over time.

At time t0, pressure as monitored by the ELCM pressure sensor (e.g.,296) is at atmospheric pressure, illustrated by plot 505, as the COV isoff, illustrated by plot 520. Such a configuration is described abovewith regard to FIG. 3C. At time t1, the ELCM pump is activated with theELCM COV off. In this example timeline, it may be understood that theELCM pump is activated in a first direction, as depicted above withregard to FIG. 3A. With the ELCM pump activated and the COV off, avacuum may be drawn on a reference orifice (e.g., 340) within the ELCM.Accordingly, between time t1 and t2, pressure as monitored by the ELCMpressure sensor becomes negative with respect to atmospheric pressure.Furthermore, between time t1 and t2, pressure as monitored by the ELCMpressure sensor is indicated to plateau. The negative pressure reachedbetween time t1 and t2 thus sets a reference vacuum level, representedby line 512. The reference vacuum level represents a threshold vacuumlevel, based on a diameter of the reference orifice. As discussed aboveand which will be discussed in further detail below, the referencevacuum level may change as a function of altitude.

At time t2, the ELCM pump is turned off, indicated by plot 515. The ELCMCOV is maintained off, indicated by plot 520. Such a configuration isdepicted above with regard to FIG. 3C. With the ELCM pump off and theCOV off, pressure as monitored by the ELCM pressure sensor returns toatmospheric pressure between time t2 and t3.

At time t3, with the reference vacuum level established, the ELCM COV isswitched from off to an on configuration, thus changing the COV from thefirst position to a second position. Furthermore, the ELCM pump is againactivated. Such a configuration is illustrated above with regard to FIG.3B. With the ELCM pump activated and the COV on, a vacuum is drawn onthe evaporative emissions control system. Accordingly, between time t3and t4, pressure as monitored by the ELCM pressure sensor becomesnegative with respect to atmospheric pressure, indicated by plot 505.Furthermore, pressure between time t3 and t4 reaches the referencevacuum level threshold, represented by plot 512. As such, it may beunderstood that the evaporative emissions control system is free fromundesired evaporative emissions. As an example, plot 510 is depicted bya dashed line in order to illustrate a condition where vacuum in theevaporative emissions control system did not reach the reference vacuumlevel threshold. In such a condition, it may be understood that theevaporative emissions control system is not free from undesiredevaporative emissions.

As discussed above, the reference vacuum level threshold may vary as afunction of altitude, as an ELCM pump may be less efficient at altitudedue to the atmospheric pressure being lower. For example, an ELCM pumpmay be able to achieve a maximum vacuum level (e.g., −13 InH₂O), at sealevel, and a substantially lower vacuum level at altitude (e.g., −9InH₂O at 8500 feet). Due to the relationship between ELCM pumpefficiency and altitude, the ELCM pump may be utilized in order to inferbarometric pressure. By inferring barometric pressure via the use of theELCM pump, other barometric pressure sensors, for example a dedicatedbarometric pressure sensor or a manifold absolute pressure (MAP) sensor(e.g., 213), may be rationalized based on vacuum level attained by theELCM pump.

Turning now to FIG. 5B, an example timeline 550 for conducting ameasurement of barometric pressure utilizing an ELCM pump, is shown.Timeline 550 includes plots 555, 560, 565, and 570, illustratingpressure as monitored by an ELCM pressure sensor (e.g., 296) at variousaltitudes, over time. Lines 556, 561, 566, and 571 represent barometricpressure(s), determined based on the pressure(s) monitored by the ELCMpressure sensor, respectively. Timeline 550 further includes plot 585,indicating whether an ELCM pump (e.g., 330) is on or off, over time.Timeline 550 further includes plot 590, indicating whether an ELCMchange over valve (COV) (e.g., 315), is in an on or off configuration,over time. Timeline 550 further includes plot 595, indicating whether avehicle key-on event is indicated, over time.

At time t0, the ELCM pump is off, indicated by plot 585, and the ELCMCOV is in an off configuration, indicated by plot 590. Such a conditionis depicted above with regard to FIG. 3C. With the COV in an offconfiguration and the ELCM pump off, the ELCM pressure sensor indicatespressure to be at atmospheric pressure.

At time t1, a key-on event is indicated. While not explicitlyillustrated, it may be understood that the key-on event may comprise avehicle-on event in electric-only mode. However, in another example thekey-on event may comprise a vehicle-on event where the engine isoperating (e.g., rotating and combusting fuel). A key-on event mayinclude a vehicle operator manually turning a key in a vehicle ignition,depressing a button on the dash in order to activate the vehicle, orremotely starting the vehicle via key fob or other smart device, forexample. At time t2, the ECLM pump is activated, with the ELCM COVmaintained in an off configuration. Such a condition is depicted abovewith regard to FIG. 3A. With the ELCM pump activated and the ELCM COVmaintained in an off configuration, vacuum may be drawn on an ECLMreference orifice (e.g., 340). Accordingly, between time t2 and t3,pressure as monitored by the ELCM pressure sensor (e.g., 296) becomesnegative with respect to atmospheric pressure. For illustrativepurposes, various negative pressure levels are shown, however it may beunderstood that, for a single ELCM-based barometric pressuremeasurement, only one negative pressure plateau may be reached. Thedepiction of various negative pressure plateau levels is meant toillustrate a number of different ELCM-based barometric pressuremeasurements conducted at different altitudes, in order to illustratethe point that different negative pressure plateaus may be reached as afunction of altitude. For example, pressure indicated by plot 555 maycomprise −13.5 InH₂O. Such a pressure level may correspond to abarometric pressure of 29 InHg, represented by line 556. In anotherexample, pressure indicated by plot 560 may comprise −12.5 InH₂O. Such apressure level may correspond to a barometric pressure of 27 InHg,represented by line 561. In another example, pressure indicated by plot565 may comprise −11.5 InH₂O. Such a pressure level may correspond to abarometric pressure of 25 InHg, represented by line 566. In stillanother example, pressure indicated by plot 570 may comprise −10.5InH₂O. Such a pressure level may correspond to a barometric pressure of23 InHg, represented by line 571. It may be understood that the examplepressures levels as indicated by the ELCM pressure sensor andcorresponding barometric pressures are meant to be illustrative, and inno way limiting. Thus, it may be understood that pressure levels asmonitored by the ELCM pressure sensor during drawing a vacuum across anELCM reference orifice may be linearly correlated with barometricpressure, such that barometric pressure measurements may be accuratelyinferred based on ELCM reference vacuum levels.

Responsive to a reference vacuum level (pressure plateau) being reached,and an inference of barometric pressure being determined based on thereference vacuum level, the ELCM pump may be commanded off, indicated byplot 585. The COV may be maintained in the off configuration, indicatedby plot 590. Accordingly, with the ECLM pump off and the COV in an offconfiguration, pressure between time t3 and t4 returns to atmosphericpressure, indicated by the various pressures depicted by plots 555, 560,565, and 570.

Turning now to FIG. 6, a high level flow chart for an example method 600for conducting an ELCM-based barometric pressure (BP) measurement torationalize another BP sensor, is shown. More specifically, method 600may be used in order to infer barometric pressure based on ELCM pumpefficiency, wherein the inferred barometric pressure may be compared tobarometric pressure indicated by another barometric pressure sensor,such as a manifold absolute pressure (MAP) sensor (e.g., 213). If BPinferred based on the ELCM-based BP measurement correlates with BPindicated by another BP sensor (e.g., MAP sensor), then it may beindicated that the BP sensor is functioning as desired. However, if theBP inferred based on the ELCM-based BP measurement does not correlatewith BP indicated by the other sensor (e.g., MAP sensor), it may beindicated that the other BP sensor is not functioning as desired.

In other words, method 600 may include indicating barometric pressurevia one or more barometric pressure sensor(s) (e.g., MAP sensor)positioned in a vehicle, activating a vacuum pump onboard the vehicle todraw a vacuum across a reference orifice of fixed diameter, determiningbarometric pressure as a function of a vacuum level reached duringactivating the onboard vacuum pump, and indicating the one or morevehicle barometric pressure sensor(s) are not functioning as desiredresponsive to barometric pressure determined as the function of thevacuum level reached during activating the onboard pump not correlatingwith barometric pressure indicated via the one or more barometricpressure sensor(s). In an example, responsive to an indication that theone or more vehicle barometric pressure sensor(s) are functioning asdesired, method 600 may include adjusting vehicle operating parametersbased on barometric pressure indicated from the one or more vehiclebarometric pressure sensor(s) during vehicle operation. In anotherexample, responsive to an indication that the one or more vehiclebarometric pressure sensor(s) are not functioning as desired, method 600may proceed to method 700 depicted in FIG. 7, wherein vehicle operatingparameters may be adjusted based on the barometric pressure determinedas the function of the vacuum level reached during activating theonboard vacuum pump.

Method 600 will be described with reference to the systems describedherein and shown in FIGS. 1-4B, though it should be understood thatsimilar methods may be applied to other systems without departing fromthe scope of this disclosure. Method 600 may be carried out by acontroller, such as controller 12 in FIG. 2, and may be stored at thecontroller as executable instructions in non-transitory memory.Instructions for carrying out method 600 and the rest of the methodsincluded herein may be executed by the controller based on instructionsstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIG. 1 and FIG. 2. The controller mayemploy fuel system and evaporative emissions control system actuators,such as canister purge valve (CPV) (e.g., 261), fuel tank isolationvalve (FTIV) (e.g., 252), ELCM pump (e.g., 330), and ELCM changeovervalve (COV) (e.g., 315), etc., according to the method below.

Method 600 begins at 605 and may include indicating whether a key-onevent is indicated. For example, as discussed above, a key-on event mayinclude a vehicle operator manually turning a key in a vehicle ignition,depressing a button on the dash in order to activate the vehicle,remotely starting the vehicle via key fob or other smart device, etc.If, at 605, a key-on event is not indicated, method 600 may proceed to610. At 610, method 600 may include maintaining vehicle-off status. Forexample, the vehicle engine and/or power from an onboard energy storagedevice may be maintained off, and fuel system and evaporative emissionscontrol system actuators may be maintained in their current status. Morespecifically, the CPV, FTIV, ELCM pump, and ELCM COV may be maintainedin their current status. Method 600 may then end.

Returning to 605, if a key-on event is indicated, method 600 may proceedto 615. At 615, method 600 may include indicating whether the key-onevent comprises a soak condition. In other words, it may be determinedif the key-on event occurred without the engine being activated. Forexample, it may be determined that the key-on event comprises an eventwhere the vehicle is activated in an electric-only mode. As discussedabove, a BP sensor measurement based on a BP sensor (e.g., 213)positioned in an intake manifold 244 of the engine may rely on partthrottle or wide open throttle (WOT) conditions in order to accuratelydetermine BP. Accordingly, if the key-on event includes engineactivation, conditions may be such that it is not practical to determineBP. In other words, throttle position at a key-on event and with theengine activation may be such that accurate BP measurement is notfeasible. Accordingly, at 615, if a soak condition (e.g., engine-offcondition) is not indicated, method 600 may proceed to 620. At 620,method 600 may include maintaining vehicle-on status, and not recordingBP at the key-on event. Maintaining vehicle-on status at 620 may includemaintaining an air intake throttle (e.g., 262) in its current position,maintaining engine operational status, and maintaining fuel system andevaporative emissions system actuators such as the CPV, FTIV, ELCM COV,and ELCM pump in their respective status. Method 600 may then end.

Returning to 615, if a soak condition is indicated, method 600 mayproceed to 625. At 625, method 600 may include recording a barometricpressure value based on the barometric pressure sensor (e.g., 213). Morespecifically, because it is indicated that the vehicle was activatedwithout engine-operation (e.g. electric-only mode), the air intakethrottle (e.g., 262) may be commanded open or maintained open, such thatan accurate indication of BP may be determined. Furthermore, withoutengine operation, accurate BP measurement may be determined by the BPsensor without the need for compensating for intake air flow. Thus, at625, BP may be determined via the BP sensor (e.g., 213), and the valuemay be stored at the controller, for example.

Proceeding to 630, method 600 may include activating the ELCM pump withthe ELCM COV in an off configuration. As discussed above with regard toFIG. 3A, and FIG. 5B, activating the ELCM pump with the COV in an off(e.g., first position) configuration, ELCM pump (e.g., 330) may drawvacuum on an ELCM reference orifice (e.g., 340). The resulting vacuumlevel (e.g., negative with respect to atmospheric pressure) may beindicated by an ELCM pressure sensor (e.g., 296). Responsive to thevacuum level reaching a plateau, method 600 may proceed to 635, and mayinclude recording the reference vacuum level. In other words, themaximum level of vacuum that can be drawn across the reference orifice,may comprise the reference vacuum level. As discussed above, thereference vacuum level may be dependent on altitude, as the ELCM pumpefficiency may decrease as a function of higher altitude with respect tosea level. The reference vacuum level recorded at 635 may be stored atthe controller, for example.

Proceeding to 640, method 600 may include de-activating the ELCM pump.In other words, the ELCM pump may be stopped from drawing a vacuumacross the reference orifice, and returned to a default, ELCM pump-offstate. With the ELCM pump deactivated, pressure as monitored by the ELCMpressure sensor may return to atmospheric pressure. While not explicitlyshown, it may be understood that the COV may be maintained in the offstate (e.g., first position). By deactivating the ELCM pump andmaintaining the COV in the off state, ELCM configuration may comprisethat depicted in FIG. 3C.

Continuing to 645, method 600 may include indicating whether thereference vacuum level determined at step 635 corresponds to the BPvalue determined at step 625. For example, as described above, a linearcorrelation may exist between reference vacuum level and barometricpressure. As such, at 645, method 600 may include the controllerconverting reference vacuum level as determined by the ELCM pressuresensor into inferred BP. For example, as discussed above, a referencevacuum level of −13.5 InH₂O may correspond to a BP of 29 InHg, areference vacuum level of −12.5 InH₂O may correspond to a barometricpressure of 27 InHg, a reference vacuum level of −11.5 InH₂O maycorrespond to a barometric pressure of 25 InHg, and a reference vacuumlevel of −10.5 InH₂O may correspond to a barometric pressure of 23 InHg.Such examples are only illustrative, and reference vacuum levels andtheir corresponding barometric pressures may vary as a function ofreference orifice (e.g., 340) diameter, ELCM pump strength, etc.Importantly, it may be understood that a linear relationship may existbetween reference vacuum level and BP for a given ELCM pump and a givenreference orifice diameter. As such, reference vacuum levels and theircorresponding BP may be included in a lookup table stored at thecontroller, such that reference vacuum level may be converted to aninferred BP by the controller at 645. Accordingly, it may thus bedetermined at 645 whether the reference vacuum level corresponds to theBP value recorded at 625 from the barometric pressure sensor (e.g.,213). In other words, it may be determined whether the inferred BP fromthe ELCM-based BP measurement correlates with the BP measurementdetermined from the BP sensor (e.g., 213). Whether the BP inferred fromthe ELCM-based BP measurement correlates with the BP measurementdetermined from the BP sensor may be based on a predetermined degree ofcloseness between the two values. For example, the ELCM-based BPmeasurement may be indicated to correlate with the BP measurement if themeasurements are within 0.1 InHg, 0.5 In Hg, or 1 InHg of each other.However, such examples are meant to be illustrative and in no waylimiting. For example, the ELCM-based BP measurement may be indicated tocorrelate with the BP measurement if the measurements are within lessthan 0.1 InHg of each other, or greater than 1.0 InHg of each other butless than another predetermined value of InHg.

If, at 645, it is indicated that the reference vacuum level (ELCM-basedBP measurement) corresponds to the BP measurement (e.g., BP sensor 213),method 600 may proceed to 650. At 650, method 600 may include indicatinga passing result of the BP rationalization test. In other words, it maybe indicated that the BP sensor (e.g., 213) is functioning as desired.In some examples, the passing result may be stored at the controller.

Proceeding to 655, method 600 may include adjusting engine operation andevaporative emissions test thresholds based on BP values determined bythe BP sensor for the duration of the vehicle drive cycle. For example,because the BP sensor (e.g., 213) was determined to be functioning asdesired, BP measurements based on the BP sensor may be continuallyupdated during the ensuing drive cycle, and engine operation adjustedaccordingly as a function of the BP measurements, provided that theengine is activated/operated during the ensuing drive cycle. Morespecifically, air/fuel ratio control and spark timing may be adjustedresponsive to BP as indicated by the barometric pressure sensor (e.g.,213). Furthermore in the event of any evaporative emissions testdiagnostic procedures that may occur during the ensuing drive cycle,thresholds corresponding to the absence or presence of undesiredevaporative emissions may be set as a function of the BP measurements.For example, some evaporative emissions test diagnostic procedures mayoccur during engine-on conditions, where engine intake manifold vacuumis utilized in order to evacuate the vehicle fuel system (e.g., 218)and/or evaporative emissions control system (e.g., 251). In such anexample, the CPV may be commanded open, the FTIV may be commanded openor in some examples maintained closed, and the ELCM COV may be turned on(e.g., switched to the second position). Pressure in the fuel systemand/or evaporative emissions control system may be monitored by a fueltank pressure transducer (e.g., 291) or the ELCM pressure sensor (e.g.,296). Responsive to a threshold vacuum (e.g. negative with respect toatmospheric pressure) being reached, the fuel system and/or evaporativeemissions control system may be sealed from engine intake by commandingclosed the CPV, and pressure bleed-up may be monitored. A pressurebleed-up rate greater than a predetermined threshold bleed-up rate, or apressure increase to a predetermined pressure threshold may within apredetermined time duration may be indicative of the presence ofundesired evaporative emissions. In such an example test diagnostic, ifthe BP sensor (e.g., 213) has been determined via method 600 to befunctioning as desired, threshold pressure bleed-up rate(s) and/orpredetermined pressure threshold(s) may be adjusted based on BP asindicated by the BP sensor. Specifically, responsive to an increase inBP (decrease in altitude), in some examples a threshold for indicatingan absence of undesired evaporative emissions may be increased tocompensate for the indicated increase in BP, and vice versa.Furthermore, in some examples, if it is indicated that BP is changingrapidly and an evaporative emissions test diagnostic is being conducted,the diagnostic may be aborted if the BP change is greater than apredetermined BP change threshold.

Returning to 645, if it is indicated that the reference vacuum level(ELCM-based BP measurement) does not correspond to the BP measurement asdetermined by the BP sensor (e.g., 213), method 600 may proceed to 660.At 660, method 600 may include indicating that the BP sensor is notfunctioning as desired. The indication that the BP sensor is notfunctioning as desired may be stored at the controller, for example. Insome examples, a malfunction indicator light (MIL) may be illuminated ona dashboard of the vehicle in order to alert the vehicle operator of theneed to service the vehicle. As the BP sensor is not functioning asdesired, method 600 may proceed to FIG. 7, where method 700 may beutilized to adjust engine operation and evaporative emissions testthresholds responsive to the indication that the BP sensor is notfunctioning as desired.

Turning now to FIG. 7, a high level flow chart for an example method 700for controlling vehicle operation responsive to an indication that a BPsensor (e.g., 213) is not functioning as desired, is shown. Morespecifically, method 700 may continue from method 600, and may includemonitoring tire pressure during vehicle operation, and, responsive toengine operation and a change in tire pressure greater than apredetermined threshold, adjusting vehicle operating conditions based onthe indicated tire pressure change.

For example, one or more tire pressure monitoring sensor(s) may becoupled to one or more tires of wheels in the vehicle. Responsive to alack of correlation between barometric pressure indicated as a functionof vacuum level during drawing vacuum across a reference orifice andbarometric pressure indicated via a barometric pressure sensor, asindicated via method 600 depicted above, method 700 may be used toindicated a change in barometric pressure during vehicle operatingconditions responsive to a tire pressure change greater than apredetermined tire pressure change threshold. In one example, method 700may include adjusting vehicle operating parameters as a function ofbarometric pressure indicated as the function of vacuum level reachedduring drawing the vacuum across the reference orifice responsive tolack of correlation between barometric pressure indicated via thebarometric pressure sensor and barometric pressure indicated as thefunction of vacuum level reached during drawing vacuum across thereference orifice, and further responsive to tire pressure change lessthan the predetermined tire pressure change threshold. In anotherexample, method 700 may include adjusting vehicle operating parametersas a function of tire pressure responsive to lack of correlation betweenbarometric pressure indicated via the barometric pressure sensor andbarometric pressure indicated as the function of vacuum level reachedduring drawing vacuum across the reference orifice, and furtherresponsive to tire pressure change greater than the predetermined tirepressure change threshold. In the examples described above, and whichwill be described in further detail below, adjusting vehicle operatingparameters may include one or more of adjusting open-loop throttleposition, adjusting spark timing, and adjusting one or more threshold(s)for evaporative emissions test diagnostic procedures.

Method 700 will be described with reference to the systems describedherein and as shown in FIGS. 1-4B, though it should be understood thatsimilar methods may be applied to other systems without departing fromthe scope of this disclosure. Method 700 may be carried out by acontroller, such as controller 212 in FIG. 2, and may be stored at thecontroller as executable instructions in non-transitory memory.Instructions for carrying out method 700 and the rest of the methodsincluded herein may be executed by the controller based on instructionsstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIG. 1 and FIG. 2. The controller mayemploy vehicle system actuators, such as canister purge valve (CPV)(e.g., 261), fuel tank isolation valve (FTIV) (e.g., 252), fuelinjectors (e.g., 266), and ELCM changeover valve (COV) (e.g., 315),etc., according to the method below.

Method 700 begins at 705 and may include monitoring tire pressure (TP)during vehicle operation subsequent to the determination (at FIG. 6)that the BP sensor (e.g., 213) is not functioning as desired. Forexample, one or more tire pressure sensors (e.g., 197) may be used tomonitor TP. The pressure sensors may be typically used in the vehicle toprovide an indication to a vehicle operator of TP in the tires so thatthe vehicle operator may be alerted if pressure in the tires becomes toolow so that air may be added to the tires. For example, if the TP in atire becomes too low then an indication may be sent to a display in thevehicle to alert the vehicle operator. In the context of method 700,tire pressure sensors may be additionally utilized to infer barometricpressure (BP) due to altitude changes in the vehicle. For example, TPmay increase responsive to increasing altitude, and may decreaseresponsive to decreasing altitude, thus providing an indication of BP.More specifically, when a vehicle begins being propelled, tire pressuremay initially increase due to friction between the tires and the groundsurface. After a duration of time, tire pressure may stabilize duringvehicle operation. If, while tire pressure has stabilized, tire pressureagain is indicated to increase or decrease greater than a predeterminedthreshold amount, it may be determined that the altitude of the vehiclehas changed, thus providing an indication of a change in BP. In someexamples, tire pressure may change more rapidly than may be expected dueto a change in altitude, for example if the tires are exposed to coldwater, or responsive to one or more tire(s) becoming depleted of air.Thus, if TP change is indicated to increase or decrease greater than thepredetermined threshold, but at a rate lower than a predeterminedthreshold rate, it may be determined that the vehicle altitude haschanged, and the TP change may be correlated with a BP change.

Proceeding to 710, method 700 may include indicating whether the engineis operating during the vehicle operation. For example, as describedabove with regard to FIG. 6, in some examples, a vehicle may bepropelled solely by energy from the onboard energy storage device (e.g.,150). However, certain driving conditions may result in the engine beingactivated. In the event that the engine is activated during vehicleoperation, engine operational strategies (e.g., air/fuel ratio estimatesand spark timing) may benefit from an accurate estimate of barometricpressure. Accordingly, in a case where the BP sensor (e.g., 213) is notfunctioning as desired, BP may be inferred from TP. Thus, at 710, ifengine operation is not indicated, method 700 may proceed to 715. At715, method 700 may include maintaining engine-off vehicle operatingconditions. For example, if the vehicle is being propelled solely by theonboard energy storage device (e.g., 150), then such vehicle operationmay be maintained.

If, at 710, engine operation is indicated, method 700 may proceed to720. At 720, method 700 may include indicating whether TP change isgreater than the predetermined threshold amount. As described above, theTP change may comprise TP change subsequent to an indication that TP hasstabilized during vehicle operation. The TP change may also comprise aTP rate of change that is not greater than the predetermined TPthreshold change rate. Accordingly, if, at 720 it is indicated that TPhas not increased or decreased greater than the predetermined thresholdamount, method 700 may proceed to 725. At 725, method 700 may includeadjusting vehicle operating conditions based on the reference vacuum(RV) level determined at FIG. 6. As described above, the RV levelachieved by activating an ELCM pump (e.g., 330) to draw vacuum across anELCM reference orifice (e.g., 340) may be linearly correlated with BP,wherein BP may be determined based on the RV level. As such, if TP isnot indicated to have changed greater than the predetermined threshold,then it may be determined that BP has not changed since the RV level wasdetermined at the vehicle start-up (described at FIG. 6). Thus, vehicleoperating conditions may be thus adjusted based on the BP determinedfrom the RV level measurement. For example, adjusting vehicle operatingconditions may include adjusting an open-loop commanded throttleposition based on the BP determined from the RV level measurement at730, and may further include adjusting spark timing at 735. Morespecifically, responsive to an indicated absence of increase/decrease inBP, the open-loop commanded throttle position may be adjusted based onthe BP indicated from the RV level. In another example, spark timing maybe adjusted as a function of BP indicated from the RV level. In stillanother example, if the vehicle is equipped with exhaust gasrecirculation (EGR), adjusting vehicle operating conditions at 725 mayinclude updating an EGR schedule. For example if the vehicle isconfigured with one or more cylinders that may route exhaust gas back tothe intake manifold in order to provide a desired dilution, then anamount of exhaust gas recirculated to the intake manifold may be basedon the BP pressure indicated from the RV level.

In a still further example, at 725, method 700 may include adjustingevaporative emissions test diagnostic thresholds. For example, asdiscussed above with regard to FIG. 6, some evaporative emissions testdiagnostic procedures may occur during engine-on conditions, whereinengine intake manifold vacuum is utilized to evacuate the vehicle fuelsystem (e.g. 218) and/or evaporative emissions control system (e.g.,251). An amount of vacuum drawn on the fuel system and/or evaporativeemissions system may be adjusted as a function of BP, for example. Morespecifically, a threshold amount of vacuum drawn on the fuel systemand/or evaporative emissions system may decrease as a function ofdecreasing BP, and increase as a function of increasing BP. Furthermore,responsive to the threshold vacuum being reached during evacuating thefuel system and/or evaporative emissions system, the system(s) may besealed from atmosphere and from engine intake (discussed above withregard to step 655 of FIG. 6), and pressure bleed-up monitored. As such,predetermined pressure threshold(s), or pressure rate thresholdsindicating the presence or absence of undesired evaporative emissionsmay decrease as a function of decreasing BP, and increase as a functionof increasing BP. Accordingly, at 740, because a change in BP was notindicated subsequent to the indication of RV level (at FIG. 6), thenevaporative emissions test diagnostic thresholds may be updated toreflect the BP pressure determined as a function of the RV level, asdiscussed above.

Proceeding to 743, method 700 may include indicating whether avehicle-off condition is indicated. Such a vehicle-off condition mayinclude a key-off event, or any other event wherein the vehicle goesfrom being in operation, to being turned off. If a vehicle-off event isindicated, method 700 may then end. Alternatively, if a vehicle-offevent is not indicated, method 700 may return to the start of method700.

Returning to 720, if it is indicated that TP change is greater than thepredetermined threshold amount, method 700 may proceed to 745. At 745,method 700 may include adjusting vehicle operating conditions based onTP change. In other words, because the BP sensor (e.g., 213) isindicated to not be functioning as desired (at FIG. 6), and based on themonitoring of TP during vehicle operation it is determined that analtitude change has occurred (BP change), the vehicle operatingconditions may be adjusted based on a BP measurement inferred from theTP change.

For example, method 700 may include adjusting an open loop commandedthrottle position to compensate for the BP change at 750 and mayadditionally or alternatively include adjusting a spark timing at 755.More specifically, responsive to an increase BP, the BP increaseindicated responsive to an indicated decrease in TP, open loop commandedthrottle position may be adjusted (e.g., toward a more closed position)to compensate for the BP change.

Alternatively, responsive to a decrease in BP, open loop commandedthrottle position may be adjusted (e.g., toward a more open position) tocompensate for the BP change. Furthermore, in another example, a moreaggressive spark timing may be employed in response to a decrease inaltitude (indicated increase in BP), whereas a less aggressive sparktiming may be employed in response to an increase in altitude (indicateddecrease in BP). In still further examples, as discussed above, if thevehicle is configured to with one or more cylinders that may routeexhaust gas back to the intake manifold to provide a desired dilution,then responsive to an increase in BP an amount of exhaust gasrecirculated to intake may be increased in order to provide the desireddilution, while responsive to a decrease in BP an amount of exhaust gasrecirculated to intake may be decreased to provide the desired dilution.

In a still further example, at 760, method 700 may include adjustingevaporative emissions test diagnostic thresholds, as discussed above.For example, an amount of vacuum drawn on the fuel system and/orevaporative emissions system during an engine-on evaporative emissionstest diagnostic may be adjusted as a function of BP, the BP inferredbased on the TP change. More specifically, a threshold amount of vacuumdrawn on the fuel system and/or evaporative emissions system maydecrease as a function of decreasing BP, and increase as a function ofincreasing BP. Furthermore, as discussed above, responsive to thethreshold vacuum being reached during evacuating the fuel system and/orevaporative emissions system, the system(s) may be sealed fromatmosphere and from engine intake (discussed above with regard to step655 of FIG. 6), and pressure bleed-up monitored. As such, predeterminedpressure threshold(s), or pressure rate thresholds indicating thepresence or absence of undesired evaporative emissions may decrease as afunction of decreasing BP, and increase as a function of increasing BP,the BP inferred based on TP. Accordingly, at 760, because BP has beenindicated to have changed subsequent to the BP indication based on RVlevel (at FIG. 6), evaporative emissions test diagnostic thresholds maybe updated/adjusted based on the BP inferred from the change in TP. Insome examples, if the indicated change in BP as inferred from the changein TP is greater than a predetermined threshold, method 700 may includeaborting any evaporative emissions test diagnostic procedures inprogress, as the results of such procedures may be unreliable responsiveto the rapid increase/decrease in BP, as inferred from the change in TP.

While not explicitly illustrated in FIG. 7, at 745, method 700 may insome examples include automatically adjusting tire pressure responsiveto an indicated tire pressure change, where the tire pressure change isa function of a change in altitude of the vehicle. For example, asdiscussed above with regard to FIG. 1, in some examples the vehicle mayinclude a pneumatic control unit (e.g., 123) that may receiveinformation regarding tire pressure from tire pressure sensor(s) (e.g.,197), wherein said tire pressure information is sent to the vehiclecontrol system (e.g., 190). Based on said tire pressure information, thecontrol system may command pneumatic control unit 123 to inflate ordeflate tire(s) (e.g., 131). By inflating or deflating said tires to anoptimal tire rating responsive to an indicated tire pressure change,lifetime of the tire(s) may be prolonged.

In such an example where tire pressure may be automatically controlledby a pneumatic control system unit (e.g., 123) responsive to indicationsof tire pressure change, control system 190 may store informationregarding tire pressure change(s), inferred barometric pressure change,and corresponding amounts of tire inflation or deflation, in order tomaintain an ability to correctly infer barometric pressure changes basedon subsequent tire pressure change(s). For example, a first tirepressure change of a specific amount may be interpreted (inferred) bythe controller as a barometric pressure change of a determined amount.The inferred barometric pressure may be stored at the controller, andtire pressure adjusted based on the indicated tire pressure change viathe pneumatic control unit system (e.g., 123). With tire pressureadjusted, further tire pressure change may thus be interpreted by thecontroller as a function of the stored barometric pressure, inferredfrom the first tire pressure change of the specific amount. In this way,barometric pressure may be accurately inferred even under circumstanceswherein tire pressure is actively adjusted based on indicated tirepressure change(s), wherein tire pressure change(s) are a function ofaltitude.

Continuing to 743, method 700 may include indicating whether avehicle-off condition is indicated. If a vehicle-off condition isindicated, method 700 may end. Alternatively, if a vehicle-off event isnot indicated, method 700 may return to the start of FIG. 7.

FIG. 8 shows an example timeline 800 for conducting an ELCM-basedbarometric pressure measurement in order to rationalize an onboardbarometric pressure sensor, according to the methods described hereinand with reference to FIGS. 6-7, and as applied to the systems describedherein and with reference to FIGS. 1-4B. Timeline 800 includes plot 805,indicating whether a vehicle key-on event is indicated (yes) or not(no), and plot 810, indicating whether an engine-on event is indicated(yes) or not (no), over time. Timeline 800 further includes plot 815,indication a position of an air intake throttle (e.g., 262), over time.Timeline 800 further includes plot 820, indicating a barometric pressureas monitored by a barometric pressure sensor (e.g., 213), over time.Timeline 800 further includes plot 825, indicating whether an ELCM pump(e.g., 330), is on or off, over time, and plot 830, indicating whetheran ELCM changeover valve

(COV) (e.g., 315) is on (e.g., second position), or off (e.g., firstposition), over time. Timeline 800 further includes plot 835, indicatinga pressure as monitored by an ELCM pressure sensor (e.g., 296), overtime. Line 836 represents a reference vacuum level, the reference vacuumlevel corresponding to an inferred barometric pressure, as describedabove and as will be described in further detail below. Timeline 800further includes plot 840, indicating a tire pressure (TP), as monitoredby one or more tire pressure sensor(s) (e.g., 197), over time. Line 841represents a first threshold TP, and line 842 represents a secondthreshold TP. Timeline 800 further includes plot 845, indicating whetherthe BP sensor (e.g., 213) is functional, over time.

At time t0, the vehicle is not in operation, as a key-on event is notindicated, illustrated by plot 805, and the engine is off, illustrate byplot 810. Throttle position is in a default vehicle-off state,illustrated by plot 815. The ELCM pump (e.g., 330) is off, illustratedby plot 825, and the ELCM COV is off, illustrated by plot 830. As such,with the ELCM pump off and the ELCM COV off (in the first position), theECLM (e.g. 295) configuration is that depicted in FIG. 3C. Accordingly,pressure as monitored by the ELCM pressure sensor (e.g., 296) is atatmospheric pressure, illustrated by plot 835. Pressure in the tires isat a baseline TP, illustrated by plot 840, where the baseline TPcomprises a level of pressure in the tires during vehicle-off conditionswherein the vehicle tires are not experiencing friction (and thus heat)responsive to ground travel, and wherein the TP is further based onenvironmental conditions. Barometric pressure, as indication by the BPsensor (e.g., 213) is near 30 InHg, indicated by plot 820. Furthermore,a BP rationalization test has not been conducted that has indicated theBP sensor to not be functioning as desired, thus the BP sensor isindicated to be functioning as desired, as illustrated by plot 845.

At time t1 a key-on event is indicated, however an engine-on event isnot indicated. As such, it may be understood that the vehicle isoperating in an electric-only mode. As the vehicle is operating in anelectric-only mode, a BP rationalization procedure may be conducted.Accordingly, at time t2, the ELCM pump is activated (in a firstdirection) with the ELCM COV maintained in the off (first position)configuration. As discussed, such a condition is depicted above withregard to FIG. 3A. With the ELCM pump activated and the ELCM COVmaintained in an off configuration, vacuum may be drawn on an ELCMreference orifice (e.g., 340). Accordingly, between time t2 and t3,pressure as monitored by the ELCM pressure sensor (e.g., 296) becomesnegative (vacuum) with respect to atmospheric pressure, and plateaus.

As discussed above responsive to the vacuum (negative pressure withrespect to atmosphere) level reaching a plateau, the reference vacuumlevel may be recorded. The reference vacuum level is represented intimeline 800 by line 836. The reference vacuum level may be stored atthe controller, for example. As discussed above, the reference vacuumlevel may be converted to a BP due to a linear relationship between BPand reference vacuum level achievable by drawing vacuum across the ELCMreference orifice. In one example reference vacuum levels and theircorresponding BP may be included in a lookup table stored at thecontroller, such that reference vacuum level may be converted to aninferred BP by the controller. In this example timeline it may beunderstood that the reference vacuum level depicted by line 836represents a BP of 23 InHg. However, the BP sensor (e.g., 213) indicatesa BP of ˜29 InHg. Thus, at time t3 it is indicated that the BP sensor isnot functioning as desired, illustrated by plot 845. Furthermore, attime t3 the ELCM pump is turned off (deactivated), while the ELCM COV ismaintained in the off configuration. With the ELCM pump turned off andthe ELCM COV in the off configuration, pressure as monitored by the ELCMpressure sensor returns to atmospheric pressure between time t3 and t4.

At time t4, the vehicle begins being propelled. While not explicitlyillustrated, it may be understood that the vehicle is being propelled ina forward direction. Accordingly, due to friction between the vehicletires and the ground surface, TP, as monitored via one or more TPsensor(s) (e.g., 197), rises and plateaus between time t4 and t5. Attime t5, the vehicle engine is turned on. For example, the vehicleengine may be activated based on vehicle operator driving conditions.More specifically, while the vehicle was being operated in electric-onlymode prior to time t5, at time t5 driving conditions may have changedsuch that power demand can only be accomplished via engine operation.

As discussed above with regard to FIG. 7, responsive to engine operationduring a vehicle drive cycle, engine operational strategies (e.g.,air/fuel ratio, spark timing, evaporative emissions test diagnosticthresholds, etc.) may benefit from an accurate estimate of barometricpressure. However, because the BP sensor (e.g., 213) was indicated tonot be functioning as desired at time t3, BP may instead be inferredbased on TP. Accordingly, responsive to engine operation, TP thresholdsmay be set, wherein, if TP change is greater than the threshold(s), thenit may be indicated that vehicle altitude has changed, and thus, achange in BP may be inferred. Accordingly, both an upper (represented byline 841), and a lower (represented by line 842) TP threshold may beset. If the upper TP threshold is reached or exceeded, then it may bedetermined that the vehicle has increased in altitude, whereas if thelower TP threshold is reached or exceeded, then it may be determinedthat the vehicle has decreased in altitude. Moreover, the extent of TPchange may be linearly correlated with BP change, similarly to therelationship discussed above with respect to reference vacuum level andBP. For example, another lookup table may be stored at the controller,wherein TP change magnitude may be correlated with BP change, such thatan accurate estimation of BP may be determined based on the TP change.

Between time t5 and t6, while the engine is in operation, driver demandfluctuates, as indicated by the throttle changing position toaccommodate increased/decreased air intake to the engine. However, TPremains plateaued within the boundaries of the upper (e.g., 841) andlower (e.g., 842) thresholds. Accordingly, a BP change is not indicated,and thus, engine operational strategies may be based on the BP inferredfrom the reference vacuum level, as discussed above. In the event that aBP change was indicated based on TP change, then engine operationalstrategies may be adjusted based on the BP inferred by the TP change, asdiscussed above. Furthermore, between time t5 and t6, the BP sensor(e.g., 213) is indicated to not change, even though throttle positionfluctuates. As such, the BP sensor may be stuck, and not responding topressure changes.

At time t6, the vehicle comes to a stop, and at time t7, a key-off eventis indicated. As such, the engine is deactivated (e.g., stopped rotatingand combusting fuel). Between time t7 and t8, with the vehicle off, TPbegins to decline, illustrated by plot 840.

While the BP rationalization procedure discussed herein with regard tomethod 600 takes place at a key-on event where an engine of the vehicleis in an off state, such a method is not meant to be limiting in anyway. For example, an inferred BP measurement utilizing the ELCM pump (orany other onboard pump for which a reference vacuum may be drawn acrossa reference orifice) may be conducted at any time during vehicleoperation, or if a vehicle is parked, wherein the inferred BPmeasurement may be compared to a last recorded BP sensor measurement.

In this way, a BP may be inferred based on a reference vacuum levelachieved by an ELCM pump, or any other pump wherein a reference vacuummay be drawn across a reference orifice such that an indication of BPmay be generated. By inferring BP using a pump, other BP sensor(s) inthe vehicle may be rationalized. By enabling vehicle BP sensor(s) to berationalized, engine operation may be improved, as engine strategies maybenefit from an accurate estimate of barometric pressure.

The technical effect is to recognize that when a constant flow pump isutilized to evacuate a small volume with a fixed diameter referenceorifice, the pump efficiency will vary as a function of altitude. Assuch, depending on the level of vacuum achieved during evacuating thesmall volume with the reference orifice, a BP may be inferred. Such aninference of BP may thus be utilized to rationalize other BP sensor(s)in the vehicle, and if the other BP sensor(s) are found to not befunctioning as desired, BP as inferred by the ELCM-based BP measurementmay be used to adjust vehicle operating conditions, such as engineoperation, and thresholds for evaporative emissions test diagnosticprocedures. A further technical effect is the ability to rationalizevehicle BP sensors without the use of engine operation, which may beparticularly useful in hybrid electric vehicles, and plug-in hybridelectric vehicles, for example. A still further technical effect is toutilize tire pressure (TP) during vehicle operation in order to infer BPresponsive to an indication that a BP sensor is not functioning asdesired. By utilizing TP to infer BP responsive to an indication that aBP sensor is not functioning as desired, pump lifetime may be extendedas the pump does not have to be used regularly to infer BP responsive toan indication that a BP sensor is not functioning as desired. Byrationalizing BP using an onboard pump such as the ELCM pump, and byfurther inferring BP based on the ELCM pump and in some examples TP,engine operation and other vehicle diagnostics such as evaporativeemissions test diagnostic procedures, which rely on accurate BPmeasurement, may be improved.

The systems described herein and with reference to FIGS. 1-4B, alongwith the methods described here and with reference to FIGS. 6-7, mayenable one or more systems and one or more methods. In one example, amethod comprises delivering fuel from a fuel system to an enginepropelling a vehicle; storing fuel vapors from the fuel system in anevaporative emissions control system; determining an estimate ofbarometric pressure as a function of an efficiency of a vacuum pumpconfigured to evacuate or pressurize the fuel system and evaporativeemissions control system; and adjusting a vehicle operating parameterresponsive to the estimate. In a first example of the method, the methodfurther comprises turning on the vacuum pump and drawing a vacuum acrossa reference orifice of fixed diameter. A second example of the methodoptionally includes the first example and further includes whereindrawing the vacuum across the reference orifice of fixed diameterincludes configuring a changeover valve coupled to the vacuum pump in afirst position; and wherein pressurizing or evacuating the vehicle fuelsystem and evaporative emissions control system includes configuring thechangeover valve in a second position. A third example of the methodoptionally includes any one or more or each of the first and secondexamples and further includes wherein the efficiency of the vacuum pumpis a function of a vacuum level achieved by the vacuum pump when drawingthe vacuum across the reference orifice of fixed diameter. A fourthexample of the method optionally includes any one or more or each of thefirst through third examples and further includes wherein efficiency ofthe vacuum pump decreases as barometric pressure decreases; and whereinthe efficiency of the vacuum pump increases as barometric pressureincreases. A fifth example of the method optionally includes any one ormore or each of the first through fourth examples and further comprisescorrelating barometric pressure determined as the function of theefficiency of the vacuum pump with barometric pressure determined fromone or more sensor(s) in the vehicle. A sixth example of the methodoptionally includes any one or more or each of the first through fifthexamples and further comprises indicating the one or more sensor(s) inthe vehicle are not functioning as desired responsive to a lack ofcorrelation between barometric pressure determined as the function ofthe efficiency of the vacuum pump and barometric pressure determinedfrom the one or more sensor(s) in the vehicle. A seventh example of themethod optionally includes any one or more or each of the first throughsixth examples and further includes wherein the one or more sensor(s) inthe vehicle include a manifold absolute pressure sensor coupled to anair intake manifold of the engine. An eighth example of the methodoptionally includes any one or more or each of the first through seventhexamples and further includes wherein adjusting a vehicle operatingparameter responsive to the estimate includes adjusting an open-loopthrottle position of a throttle coupled to an air intake manifold of theengine to a more closed position responsive to an increase in barometricpressure, and adjusting the open-loop throttle position to a more openposition responsive to a decrease in barometric pressure. A ninthexample of the method optionally includes any one or more or each of thefirst through eighth examples and further includes wherein adjusting avehicle operating parameter responsive to the estimate includesadjusting timing of a spark provided to one or more engine cylinder(s);wherein adjusting timing of the spark includes more aggressive sparktiming responsive to barometric pressure increase, and less aggressivespark timing responsive to barometric pressure decrease. A tenth exampleof the method optionally includes any one or more or each of the firstthrough ninth examples and further includes wherein adjusting a vehicleoperating parameter responsive to the estimate further comprisesadjusting an evaporative emissions test diagnostic threshold. Aneleventh example of the method optionally includes any one or more oreach of the first through tenth examples and further includes whereinthe estimate of barometric pressure is determined without operation ofthe vehicle engine.

Another example of a method comprises indicating barometric pressure viaone or more barometric pressure sensor(s) positioned in a vehicle;activating a vacuum pump onboard the vehicle to draw a vacuum across areference orifice of fixed diameter; determining barometric pressure asa function of a vacuum level reached during activating the onboardvacuum pump; and indicating the one or more vehicle barometric pressuresensor(s) are not functioning as desired responsive to barometricpressure determined as the function of the vacuum level reached duringactivating the onboard vacuum pump not correlating with barometricpressure indicated via the one or more barometric pressure sensor(s). Ina first example of the method, the method further includes wherein thevacuum level reached during activating the onboard vacuum pump to drawthe vacuum across the reference orifice is linearly correlated withbarometric pressure; wherein as barometric pressure increases, thevacuum level reached during activating the onboard vacuum pumpincreases; and wherein as barometric pressure decreases, the vacuumlevel reached during activating the onboard vacuum pump decreases. Asecond example of the method optionally includes the first example andfurther comprises responsive to an indication that the one or morevehicle barometric pressure sensor(s) are functioning as desired;adjusting vehicle operating parameters based on barometric pressureindicated from the one or more vehicle barometric pressure sensor(s)during vehicle operation. A third example of the method optionallyincludes any one or more or each of the first and second examples andfurther comprises responsive to an indication that the one or morevehicle barometric pressure sensor(s) are not functioning as desired;adjusting the vehicle operating parameters based on the barometricpressure determined as the function of the vacuum level reached duringactivating the onboard vacuum pump. A fourth example of the methodoptionally includes any one or more or each of the first through thirdexamples and further includes wherein the adjusting vehicle operatingparameters includes one of at least: adjusting an open-loop throttleposition of a throttle coupled to an air intake manifold of an engine ofthe vehicle, adjusting timing of spark provided to one or more cylindersof the engine, and adjusting one or more threshold(s) for an evaporativeemissions test diagnostic procedure; where the evaporative emissionstest diagnostic procedure includes evacuating a fuel system and/or anevaporative emissions control system of the vehicle, and monitoring apressure bleed-up subsequent to sealing the fuel system and/orevaporative emissions control system.

An example of a system for a vehicle comprises a fuel system including afuel tank that supplies fuel to a vehicle engine; an evaporativeemissions control system, selectively coupled to the fuel tank via afuel tank isolation valve, and including a fuel vapor storage canister;an evaporative level check module (ELCM) positioned in a conduit betweenthe fuel vapor storage canister and atmosphere, where the ELCM includesan electrically driven pump, a changeover valve operable between anfirst and a second position, and a reference orifice; an intake manifoldof the vehicle engine; a barometric pressure sensor positioned in theintake manifold of the vehicle engine; and a controller storinginstructions in non-transitory memory, that when executed, cause thecontroller to: while the engine is off; indicate barometric pressure viathe barometric pressure sensor positioned in the intake manifold of thevehicle engine; configure the changeover valve in the first position andactivate the pump to draw a vacuum across the reference orifice;indicate barometric pressure as a function of vacuum level reachedduring drawing the vacuum across the reference orifice; and indicate thebarometric pressure sensor is functioning as desired responsive tobarometric pressure indicated as the function of vacuum level reachedduring drawing the vacuum across the reference orifice correlating withbarometric pressure indicated via the barometric pressure sensor. In afirst example, the system further comprises one or more tire pressuremonitoring sensor(s) coupled to one or more tires of wheels in thevehicle; wherein the controller further stores instructions innon-transitory memory, that when executed, cause the controller to:responsive to a lack of correlation between barometric pressureindicated as the function of vacuum level during drawing the vacuumacross the reference orifice and barometric pressure indicated via thebarometric pressure sensor; monitor tire pressure via the one or moretire pressure monitoring sensor(s); and indicate a change in barometricpressure during vehicle operating conditions responsive to a tirepressure change greater than a predetermined tire pressure changethreshold. A second example of the system optionally includes the firstexample and further includes wherein the controller further storesinstructions in non-transitory memory, that when executed, cause thecontroller to: adjust vehicle operating parameters as a function ofbarometric pressure indicated via the barometric pressure sensorresponsive to the indication that the barometric pressure sensor isfunctioning as desired; adjust vehicle operating parameters as afunction of barometric pressure indicated as the function of vacuumlevel reached during drawing the vacuum across the reference orificeresponsive to lack of correlation between barometric pressure indicatedvia the barometric pressure sensor and barometric pressure indicated asthe function of vacuum level reached during drawing vacuum across thereference orifice, and further responsive to tire pressure change lessthan the predetermined tire pressure change threshold; and adjustvehicle operating parameters as a function of tire pressure responsiveto the lack of correlation between barometric pressure indicated via thebarometric pressure sensor and barometric pressure indicated as thefunction of vacuum level reached during drawing vacuum across thereference orifice, and further responsive to tire pressure changegreater than the predetermined tire pressure change threshold; whereinadjusting vehicle operating parameters includes one or more of adjustingopen-loop throttle position, adjusting spark-timing, and adjusting oneor more threshold(s) for evaporative emissions test diagnosticprocedures.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

1. A method for operating a hybrid-electric vehicle, comprising: drivingvehicle wheels with an electric motor; delivering fuel from a fuelsystem to an engine propelling the vehicle wheels; storing fuel vaporsfrom the fuel system in an evaporative emissions control system;determining an estimate of barometric pressure as a function of anefficiency of a vacuum pump configured to evacuate or pressurize thefuel system and evaporative emissions control system; and adjusting avehicle operating parameter responsive to the estimate.
 2. The method ofclaim 1, wherein the vehicle is a plug-in hybrid-electric vehicle. 3.The method of claim 1, wherein the fuel system has a fuel cap with afuel cap locking mechanism configured to automatically lock the fuel capin a closed position, the fuel cap remaining locked via a refueling lockwhile pressure or vacuum in a fuel tank of the fuel system is greaterthan a threshold, the method further comprising, in response to a refuelrequest by an operator, depressurizing the fuel tank and then unlockingthe fuel cap unlocked after the pressure or vacuum in the fuel tankfalls.
 4. The method of claim 1, further comprising: turning on thevacuum pump and drawing a vacuum across a reference orifice of fixeddiameter, wherein drawing the vacuum across the reference orifice offixed diameter includes configuring a changeover valve coupled to thevacuum pump in a first position; and wherein pressurizing or evacuatingthe vehicle fuel system and evaporative emissions control systemincludes configuring the changeover valve in a second position.
 5. Themethod of claim 4, wherein the efficiency of the vacuum pump is afunction of a vacuum level achieved by the vacuum pump when drawing thevacuum across the reference orifice of fixed diameter.
 6. The method ofclaim 1, wherein efficiency of the vacuum pump decreases as barometricpressure decreases; and wherein the efficiency of the vacuum pumpincreases as barometric pressure increases.
 7. The method of claim 1,further comprising: correlating barometric pressure determined as thefunction of the efficiency of the vacuum pump with barometric pressuredetermined from one or more sensor(s) in the vehicle, and indicating theone or more sensor(s) in the vehicle are not functioning as desiredresponsive to a lack of correlation between barometric pressuredetermined as the function of the efficiency of the vacuum pump andbarometric pressure determined from the one or more sensor(s) in thevehicle.
 8. The method of claim 7, wherein the one or more sensor(s) inthe vehicle include a manifold absolute pressure sensor coupled to anair intake manifold of the engine.
 9. The method of claim 1, whereinadjusting a vehicle operating parameter responsive to the estimateincludes adjusting an open-loop throttle position of a throttle coupledto an air intake manifold of the engine to a more closed positionresponsive to an increase in barometric pressure, and adjusting theopen-loop throttle position to a more open position responsive to adecrease in barometric pressure.
 10. The method of claim 1, whereinadjusting a vehicle operating parameter responsive to the estimateincludes adjusting timing of a spark provided to one or more enginecylinder(s); wherein adjusting timing of the spark includes moreaggressive spark timing responsive to barometric pressure increase, andless aggressive spark timing responsive to barometric pressure decrease.11. The method of claim 1, wherein adjusting a vehicle operatingparameter responsive to the estimate further comprises adjusting anevaporative emissions test diagnostic threshold.
 12. The method of claim1, wherein the estimate of barometric pressure is determined withoutoperation of the vehicle engine but while the vehicle operates in anelectric mode.
 13. A method of operating a hybrid-electric vehicle,comprising: driving vehicle wheels with an electric motor via storedelectrical energy; indicating barometric pressure via one or morebarometric pressure sensor(s) positioned in the vehicle; activating avacuum pump onboard the vehicle to draw a vacuum across a referenceorifice of fixed diameter; determining barometric pressure as a functionof a vacuum level reached during activating the onboard vacuum pump; andindicating the one or more vehicle barometric pressure sensor(s) are notfunctioning as desired responsive to barometric pressure determined asthe function of the vacuum level reached during activating the onboardvacuum pump not correlating with barometric pressure indicated via theone or more barometric pressure sensor(s), wherein the indication ofbarometric pressure sensor functioning is carried out without the use ofengine operation.
 14. The method of claim 13, wherein the vacuum levelreached during activating the onboard vacuum pump to draw the vacuumacross the reference orifice is linearly correlated with barometricpressure; wherein as barometric pressure increases, the vacuum levelreached during activating the onboard vacuum pump increases; and whereinas barometric pressure decreases, the vacuum level reached duringactivating the onboard vacuum pump decreases.
 15. The method of claim13, further comprising: responsive to an indication that the one or morevehicle barometric pressure sensor(s) are functioning as desired;adjusting vehicle operating parameters based on barometric pressureindicated from the one or more vehicle barometric pressure sensor(s)during vehicle operation.
 16. The method of claim 15, furthercomprising: responsive to an indication that the one or more vehiclebarometric pressure sensor(s) are not functioning as desired; adjustingthe vehicle operating parameters based on the barometric pressuredetermined as the function of the vacuum level reached during activatingthe onboard vacuum pump.
 17. The method of claim 16, wherein theadjusting vehicle operating parameters includes one of at least:adjusting an open-loop throttle position of a throttle coupled to an airintake manifold of an engine of the vehicle, adjusting timing of sparkprovided to one or more cylinders of the engine, and adjusting one ormore threshold(s) for an evaporative emissions test diagnosticprocedure; where the evaporative emissions test diagnostic procedureincludes evacuating a fuel system and/or an evaporative emissionscontrol system of the vehicle, and monitoring a pressure bleed-upsubsequent to sealing the fuel system and/or evaporative emissionscontrol system.
 18. A system for a plug-in hybrid-electric vehicle,comprising: an electric motor configured to drive vehicle wheels a fuelsystem including a fuel tank that supplies fuel to a vehicle engine; anevaporative emissions control system, selectively coupled to the fueltank via a fuel tank isolation valve, and including a fuel vapor storagecanister; an evaporative level check module (ELCM) positioned in aconduit between the fuel vapor storage canister and atmosphere, wherethe ELCM includes an electrically driven pump, a changeover valveoperable between an first and a second position, and a referenceorifice; an intake manifold of the vehicle engine; a barometric pressuresensor positioned in the intake manifold of the vehicle engine; and acontroller storing instructions in non-transitory memory, that whenexecuted, cause the controller to: while the engine is off; indicatebarometric pressure via the barometric pressure sensor positioned in theintake manifold of the vehicle engine; configure the changeover valve inthe first position and activate the pump to draw a vacuum across thereference orifice; indicate barometric pressure as a function of vacuumlevel reached during drawing the vacuum across the reference orifice;and indicate the barometric pressure sensor is functioning as desiredresponsive to barometric pressure indicated as the function of vacuumlevel reached during drawing the vacuum across the reference orificecorrelating with barometric pressure indicated via the barometricpressure sensor, wherein the instructions for indicating barometricpressure are carried out without the operating of the engine.
 19. Thesystem of claim 18, further comprising: one or more tire pressuremonitoring sensor(s) coupled to one or more tires of wheels in thevehicle; wherein the controller further stores instructions innon-transitory memory, that when executed, cause the controller to:responsive to a lack of correlation between barometric pressureindicated as the function of vacuum level during drawing the vacuumacross the reference orifice and barometric pressure indicated via thebarometric pressure sensor; monitor tire pressure via the one or moretire pressure monitoring sensor(s); and indicate a change in barometricpressure during vehicle operating conditions responsive to a tirepressure change greater than a predetermined tire pressure changethreshold.
 20. The system of claim 19, wherein the controller furtherstores instructions in non-transitory memory, that when executed, causethe controller to: adjust vehicle operating parameters as a function ofbarometric pressure indicated via the barometric pressure sensorresponsive to the indication that the barometric pressure sensor isfunctioning as desired; adjust vehicle operating parameters as afunction of barometric pressure indicated as the function of vacuumlevel reached during drawing the vacuum across the reference orificeresponsive to lack of correlation between barometric pressure indicatedvia the barometric pressure sensor and barometric pressure indicated asthe function of vacuum level reached during drawing vacuum across thereference orifice, and further responsive to tire pressure change lessthan the predetermined tire pressure change threshold; and adjustvehicle operating parameters as a function of tire pressure responsiveto the lack of correlation between barometric pressure indicated via thebarometric pressure sensor and barometric pressure indicated as thefunction of vacuum level reached during drawing vacuum across thereference orifice, and further responsive to tire pressure changegreater than the predetermined tire pressure change threshold; whereinadjusting vehicle operating parameters includes one or more of adjustingopen-loop throttle position, adjusting spark-timing, and adjusting oneor more threshold(s) for evaporative emissions test diagnosticprocedures.